Production of ammonium sulphate



INVENTOR 64/FL07'71O /Jaflfi? a ATTORNEY Filed Feb. 10, 1943 PatentedJuly 15, 1947 PRODUCTION OF AMNIONIUM SULPHA'I'E Carl Otto, Manhasset,N. Y., assignor to Fuel Refining Corporation, New York, N. Y., acorporation of Delaware Application February 10, 1943, Serial No.475,371

Claims.

The present invention relates to apparatus for recovering ammonia fromdistillation gas by passing the gas through a so called saturator tankholding in its lower portion a weak sulphuric acid liquor bath withwhich the gas is brought into scrubbing contact with the resultantproduction of sulphate of ammonia which crystallizes out of the bathliquor and accumulates in the lower portion of the saturator, and fromwhich the sulphate crystals are removed in a carrying stream of liquor.In practice, the scrubbing contact of the gas with the bath liquor iseffected by passing the gas into the saturator through a so calledcracker pipe which has a discharge mouth submerged in the bath liquor.

In the use of such a saturator, particularly when the bath liquor hasthe relatively low acid content required for the production of largecrystals of sulphate of ammonia, troublesome sulphate of ammoniadeposits, commonly called rock salt, form on the internal surfaceportions of the saturator. Such salt formations are wholly or mainly theresult of the dehydrating action of the gas on drops and films of bathliquor splashed or otherwise deposited on portions added gas does notchange the composition of the of the saturator surface with which thegas comes s passi g y from the saturator. in practice into contact. theamount of air added to the steam to prevent In my prior applications,Serial Nos. 473,949 water hammer is too small to have any significantand 473,951, filed January 29, 1943, I have diseffect p e composition ofthe gas leavin closed arrangements for injecting Water or other thesaturator. liquor into the saturator gas space which are h S eaminjected into the bath liquor to effective to substantially minimizesalt formaovoid o je t onab e Salt deposits as above 618- tions on thebulk of the internal saturator surd. serves also t s pp y t t a h l quorface in contact with the gas passing through the in a relatively in pand Convenient saturator. I have discovered, however, that the nor heatwhich is needed to maintain a suitably arrangements described in myprior application high bath temperature tw s a d the are not alwayseffective to prevent objectionable action of the gas treated in evaporag water salt deposits on the portion of the inner wall of out of thebath q or and t e eby coolin th the saturator tank adjacent the bathlevel. Salt latter. deposits on that portion of the tank wall areAdvantageously, the jets of steam and air or especially apt to occur infull load operation of a s inj cted i o t e th q r e directed relativelylarge saturator with the relatively low to create a continuous c a e e tof t e bath acidity required for the production of large bath liquoraround the S of the Saturator a ammonium sulphate crystals, inconsequence of or to augment the circular movement of the bath v therelatively violent splashing of the bath liquor liquor about Said SWhich t gas passing out against the portion of the saturator Wallimmediof the cracker pipe discharge mouth may produce ately above thebath level and the up and down When d dis mouth s s y s p d movement ofthe top surface of the bath liquor folthe P in contact with the tankwall, resulting fro the A further object of the present invention is toscrubbing contact of the as and bath liquor. to prov d p d means forpreventing salt A main object of the present invention is to posits onthe saturator surfaces above and out. provide novel and efiective meansfor minimizing of direct contact with the bath held in the lower orpreventing troublesome salt formation on the position of the saturator.portion of the saturator tank wall adjacent the The various features ofnovelty which charnormal bath level. To attain this object, I 10-:aeterize my invention are pointed out with parcally heat the bath liquorimmediately adjacent the portion of the tank wall intersected by thebath level. To thus heat the portion of the bath liquor adjacent saidwall, I inject jets of steam into said portion of the bath liquor, bywhich the injected steam is condensed. By thus heating the bath liquorin contact with the tank wall adjacent the top of the bath, the capacityof that liquor to dissolve sulphate of ammonia and to hold the latter insolution is increased and that capacity i further increased by the localdilution of the bath liquor resulting from the addition thereto of thewater of condensation formed.

To avoid Water hammer eiiects, I advantageously mix compressed air orgas with the steam injected into the liquor. The addition of air or gasto the steam is beneficial, also, in that it results in an increase inthe volume of the gaseous fluid injected into the-bath liquor andthereby augments the scrubbing action of the bath liquor on the adjacentportion of the tank wall. While the addition of distillation gas istheoretically preferable to the addition of air to the steam injectedinto the bath liquor because the ticularity in the claims annexed to andforming a part of this specification. For a better understanding of theinvention, however, its advantages, and specific objects attained withits use, reference should be had to the accompanying drawing anddescriptive matter in which I have illustrated and described preferredembodiments of the invention.

f the drawings:

Fig. 1 is an elevation in section of a saturator;

Fig. 2 is a plan in section on the line 2-2 of Fig. 1; and

Fig. 3 is an enlarged section on the line 3--3 of Fig. 2.

In the drawings I have illustrated an embodiment of the presentinvention in a saturator comprising a tank A of conventional form andconstruction, provided with a vertical centrally disposed cracker pipe Bhaving a separately formed discharge mouth piece B suitably attached toits lower end and submerged in the bath liquor filling the lower portionof the tank to its overflow level A. The cracker pipe B receives gas atits upper end through the outlet C from a gas inlet chamber C receivinggas from a supply main C The gas flowing downward through the crackerpipe passes into scrubbing contact with the bath liquor and thenceupward away from the bath into the annular gas space above the bathlevel A and surrounding the cracker pipe B, and passes away from thatgas space through the gas discharge pipe D. The bath liquor level A isdetermined by the position of a weir E, advantageously adjustable, in abath liquor overflow outlet E. As shown, the latter comprises adepending conduit portion extending down into a tar separator F of knowntype including a chamber from the top of which tar may be skimmed orotherwise removed. The separator F has an outlet F for the tar free bathliquor. Bath liquor withdrawn from the saturator may be returned througha pipe G and also through other pipes Q and S hereinafter referred to.

Ammonium sulphate crystals accumulating in the lower portion of the bathare withdrawn from the latter in a carrying stream of bath liquor bysuitable means shown as comprising a pipe I-I, having an inlet branch Hcommunicating with the tank at the apex of its hopper bottom portion.Customarily, the pipe H leads to the inlet of a suitable pump (notshown), by which the bath crystals and the crystal enveloping bathliquor are delivered to suitable crystal drying apparatus. As shown, aspray pipe ring I surrounds the cracker pipe adjacent its upper end andis adapted to spray liquid against the inner tank wall and externalcracker pipe surfaces, to thereby wash ofi sulphate of ammonia splashedagainst the said surfaces from the bath, and passing out of entrainmentin the gas coming into contact with said surfaces as it passes upwardfrom the bath to the gas outlet D. The wash liquid is supplied to thespray pipe I through a supply pipe I at a rate which may be regulated bythe adjustment of a valve 1 The wash liquid supplied to the spray ring Imay well be hot water though in some cases it may be bath liquor, and ineither event may include makeup acid which must be supplied to the bathto make up for the acid converted into sulphate of ammonia. As shown themake-up acid is supplied through a pipe J discharging into the supplypipe I.

In accordance with the present invention bath heating fluid is injectedinto the bath adjacent its periphery and a few inches below the bathlevel A, through a multiplicity of pipes K distributed about the tankaxis. Each pipe K in the form shown in the drawings, comprises ahorizontal portion extending through the saturator tank wall andconnected at its outer end to a manifold L extending circularly aboutthe saturator tank B. Each spray pipe K comprises a down-turned portionK within the tank and a horizontal discharge end portion K extendingsubstantially at right angles to an adjacent plane including the commonaxis of the cracker pipe B and tank A.

The heating fluid injected may advantageously be supplied at a pressureof only a pound or so above atmospheric pressure. As shown in Fig. 1,the fluid supplied to the manifold L is steam mixed with distillationgas by means of a steam injector M to which steam is supplied by a pipeM and having a mixing chamber receiving gas from the saturator gasoutlet D through a pipe M As shown, the cracker pipe mouth piece B isoutwardlyfiared and is provided at its underside with ribs B whichextend inward from the rim of the mouthpiece and are curved, as shown inFig. 2, two discharge gas streams each having a substantial flowcomponent in a direction tangential to the rim of the mouthpiece. Inconsequence said gas streams create a circulatory movement of the bathliquor adjacent the top of the bath about the saturator axis which is inthe clockwise direction when the ribs 13 are curved as shown in Fig. 2.Advantageously, and as shown, the discharge ends K of the pipes K are sodirected relative to the direction in which the outer ends of the ribs13 diverge from planes radial to the cracker pipe axis that the bathliquor circulation induced by the pipe ends K and that induced by thegas streams defined by the curved ribs B are in the same direction,which as shown in Fig. 2, is clockwise.

In the contemplated mode of use of the present invention steam issupplied by the pipe M at such temperature and in such volume relativeto the saturator bath volume and temperature, that substantially all ofthe steam injected into the bath liquor is condensed therein and theportion of the bath liquor into which the steam is injected is therebymaintained at a temperature somewhat above the average temperature ofthe saturator bath.

By thus heating the bath liquor in contact with the tank wall adjacentthe top of the bath, the capacity of that portion of the bath liquor tohold sulphate of ammonia in solution is appreciably increased, and thepossibility that crystallized sulphate will deposit on the portion ofthe tank wall by such liquid is correspondingly reduced. The possibleoccurrence of such deposits is further reduced as a result of thedilution of the portion of the bath liquor into which the steam isinjected by the water of condensation formed, and is further reduced bythe scrubbing action on the wall of the bath liquor due to its agitationby the jets discharged through the pipes K. The gas mixed with the steamdischarged through said pipes serves to increase the volumeand sombbingefiect of the jets in addition to serving its primary purpose ofpreventing water hammer vibration noise.

As previously explained, the heat added to the bath by the steaminjected into the latter raises the average bath temperature and thusreduces the quantity of heat which must be constantly added to the bath,in many cases, to avoid an unduly low temperature of the gas liquorwhich is subjected to the cooling effect of the evaporation of the waterout of the bath by the gas passing through th saturator.

While the injection of hot water into the saturator through the spraypipe ring I at a suitable rate will substantially retard the formationof sulphate deposits upon the upper portions of the inner surface of thesaturator wall and on the outer surface of the cracker pipe, it is notpractically feasible to supply enough wash water through the spray pipeI to prevent sulphate deposits on the exposed upper surface of thesaturator, without risk of killing the bath, i. e., of reducing the acidcontent of the gas to an extent which prevents sulphate of ammonia fromcrystallizing out of the bath liquor.

In the construction shown in Fig. 1, the means for avoiding sulphatedeposits on the upper saturator surfaces comprises a spray pipe as wellas the previously mentioned spray pipe I. The pipe 0 extends circularlyabout the axis of the saturator adjacent the upper end of the inner sideof th cylindrical body portion of the tank wall. As shown, heated bathliquor is supplied to the spray pipe 0 by means of a pump P which drawstar-free liquor from the tar separator F through its outlet pipes F anddischarges the bath liquor through a pipe P into a suitable heater Qfrom which the heated bath liquor passes through a pipe Q to the spraypipe 0. In the simple and relatively inexpensive form illustrated, theheater Q comprises an enclosed chamber through which the liquor receivedfrom the pipe P' passes to the discharge pipe Q, and in which the liquoris heated by direct contact with a mixture of steam anad non-condensiblegas passed into the chamber through a tubular element R. The latter, inthe simple form shown somewhat diagrammatically in Fig. 1, comprises amixing chamber open at one end to the heating chamber and at its otherand closed end, receives steam through a supply pipe R, and anon-condensible gas through a pipe R The non-condensible gas supplied bythe pipe R, may be compressed air or distillation gas. As will beapparent, the liquor heating operation effected by the steam and airmixture discharged into the heater Q through the element R is identicalin principle with that effected by discharging a steam and gas mixtureinto the saturator bath through the pipes K. In each case the steam iscondensed in, and the water of condensation formed is mixed with theliquor heated, and in each case non-condensible gas mixed with the steamsubstantially prevents the water hammer shock or vibration and noisecommonly experienced when steam is discharged into the water at a lowertemperature through a submerged nozzle.

The eflect of heating the gas liquor passing through the spray pipe 0 isto increase the capacity of the liquor to hold sulphate of ammonia insolution. It is practically feasible to supply heated bath liquorthrough the pipe 0 in the manner described in such volume and at atemperature sufficiently above the saturator bath temperature toentirely prevent sulphate deposits on the saturator surfaces washed bythat liquor whil also supplying enough steam to the saturator throughthe pipes K for their intended operative effect without risk of anobjectionable dilution of the bath or an objectionable increase in thebath temperature. As will be apparent, the amount of bath liquor sprayedinto the spray pipe 0 will ordinarily have no significant effect on thestrength of the saturator bath.

As will be apparent, the supply pipe I may also be supplied with bathliquor through the heater Q. In many cases, however, it will bepractically convenient and desirable to .supply water, preferably hot,to the spray pipe I, in amounts sufiicient to prevent sulphate depositson the outer surface of the cracker pipe and on the portion of thesaturator tank roof adjacent the spray pipe 0, while supplying heatedbath liquor to the spray pipe 0 in amounts suflicient to prevent rocksalt deposits on the inner saturator wall surfaces washed by the sprayfrom the pipe 0. Advantageously, and as shown, the'connection flange BOn the adjacent ends of the cracker pipe body and mouth piece B are atthe inner side of the cracker pipe and mouth piece, so that the outersurfaces of the cracker pipe and its mouth piece are smooth and opposeno obstacles to the maintenance of a continuous downflowing film of thewash water discharged against the upper end of the cracker pipe by thespray pipe I.

As shown in Fig. '1, the pipe S returns bath liquor to the saturatorthrough a tangential inlet S formed in the hopper bottom portion of thesaturator tank wall. The liquor returned to the saturator through theinlet S may come from any one or more of the usual sources of liquorwithdrawn from the saturator. Preferably, the rate at which liquor isreturned through the inlet S is sufficiently in excess of the rate atwhich liquor is withdrawn from the saturator through the pipe P, so thatthere is an appreciable flow of liquor upward from the level of theinlet 8-. The circularly and upwardly directed flow of liquor in thelower portion of the saturator due to the liquor return through theinlet S, creates a barrier or baffle which materially minimizes thegravitational downflow to the pipe H of fine sulphate crystals, withoutoffering similarly minimizing opposition to the downflow of the largercrystals. As shown in Fig. 1, the usual brick lining for th lowerportion of the metallic saturator tank wall, is cut away to provide asmooth walled space of suitable size for the circulation created by thereturn of liquor through the inlet S.

Novel features disclosed herein and operating to prevent fine crystalsfrom moving freely with the larger crystals to the inlet of the crystalwithdrawing conduit H, which are disclosed but not claimed herein, areclaimed in my copending application Serial No. 492,265, filed June 25,1943.

While in accordance with the provisions of the statutes, I haveillustrated and described the best forms of embodiment of my inventionnow known to me, it will be apparent to those skilled in the art thatchanges may be made in the forms of the apparatus disclosed withoutdeparting from the spirit of my invention as set forth in the appendedclaims, and that in, some cases certain features of my invention may beused to advantage without a corresponding use of other features.

Having now described my invention what I claim as new, and desire tosecure by Letters Patent is:

1. In the production of sulphate of ammonia crystals in a saturator inwhich a bath of sulphuric acid is maintained at the bottom of the tankand a gas space above the bath, the method which comprises passingammonia containing gas through said saturator and into scrubbing contactwith the bath liquor therein and thence through said gas space, andminimizing salt deposits on the portion of the tank wall adjacent thelevel of its intersection with the top surface of the bath by heatingthe portion of the bath immediately adjacent said wall to a temperatureabove the average temperature of the bath by injecting steam into saidportion of the bath.

2. In the production of sulphate ammonia crystals in a saturator inwhich a bath of sulphuric acid is maintained at the bottom of the tankand a gas space abovethe bath, the method which comprises passingammonia containing gas through said saturator and into scrubbing contactwith the bath liquor therein and thence through said gas space, andminimizing salt deposits on the portion of the tank wall adjacent thelevel of its intersection with the top surface of the bath by heatingthe portion of the bath immediately adjacent said wall to a temperatureabove the average temperature of the bath by injecting into the portionof the bath thus heated steam admixed with a non-condensible gas whichminimizes vibration and noise resulting from the condensation of thesteam.

3. In the production of sulphate of ammonia crystals in a saturator inwhich a bath of sulphuric acid is maintained at the bottom of the tankand a gas space above the bath, the method which comprises passingammonia containing gas into scrubbing contact with the bath liquor inthe central upper portion of the bath and thence into and through saidgas space in such manner as to create a. circular movement of said bathliquor about a vertical axis extending centrally through the tank andinjecting heating fluid jets into the upper portion of the bath liquoradjacent the tank wall to thereby heat the last mentioned bath liquor toa temperature above the average bath temperature and to augment thecirculation of bath liquor about said axis.

4. Apparatus for producing sulphate of ammonia by scrubbing contact ofdistillation gas with sulphuric acid liquor comprising in combination asaturator shell adapted to contain a bath of sulphuric acid in the lowerportion thereof and having a withdrawal pipe constructed and located soas to establish an intermediate level of liquid downwardly into saidshell and having a flared mouth below said intermediate level, inletmeans for gases into said pipe, and liquid heating means within andextending about the axis of the shell and disposed in an annular portionof the space therein adjacent the wall of the said shell and below butadjacent said intermediate level.

5. Apparatus for producing sulphate of ammonia by scrubbing contact ofdistillation gas with sulphuric acid liquor comprising in combination asaturator shell adapted to contain a bath of sulphuric acid in the lowerportion thereof and having a withdrawal pipe constructed and located soas to establish an intermediate level of liquid therein, a verticallydisposed pipe extending downwardly into said shell and having a. flaredmouth below said intermediate level, inlet means for gases into saidpipe, a liquid heating means comprising conduit means within said shelland having outlet openings for the discharge of a heating fluiddistributed about the axis of said shell and located in an annularportion of the space within the shell and adjacent the wall of saidshell and inlet means for the passage of a heating fluid into saidconduit means.

CARL OTTO.

REFERENCES CITED The following references are of record in the file ofthis'patent:

UNITED STATES PATENTS OTHER REFERENCES Bell, Methods for the Improvementof By- Product Sulphate of Ammonia, printed in the Gas World, December3, 1938, page 18.

